1. Field of the Invention
The present invention relates to a combustion-type exhaust gas treatment apparatus for treating a harmful and combustible exhaust gas, which contains, for example, silane gas (SiH4) or halogen gas (NF3, ClF3, SF6, CHF3, C2F6, CF4, or the like), by combustion so as to render the exhaust gas harmless.
2. Description of the Related Art
A semiconductor fabrication apparatus discharges a gas including a harmful and combustible exhaust gas, e.g., silane gas (SiH4) or halogen gas (NF3, ClF3, SF6, CHF3, C2F6, CF4). Such an exhaust gas cannot be released as it is into the atmosphere. Thus, the exhaust gas is generally introduced to a treatment apparatus, where the exhaust gas is oxidized by combustion so as to be rendered harmless. A widely-used treatment process of this type is such that a combustion-supporting gas is used to form flames in a furnace in which the exhaust gas is combusted by the flames, as seen in Japanese laid-open patent publication No. 11-218317.
A combustion-type exhaust gas treatment apparatus for use in a semiconductor industry and a liquid crystal industry potentially discharges a large amount of dust (mainly SiO2) and a large amount of an acid gas as by-products of combustion treatment of the exhaust gas. Consequently, a regular maintenance operation is required so as to remove the dust from a treatment section, or an additional mechanism, such as a scraper, is required so as to regularly scrape away the dust attached to and deposited on an inner surface of a cylindrical body of a combustion treatment chamber.
The dust attached and deposited is composed mainly of SiO2 (i.e., silicon dioxide). Other than SiO2, however, the dust may probably have toxic dust mixed therewith. The dust has various diameters ranging from 0.1 micrometers to several tens of micrometers. Moreover, the dust may exist as large blocks. Consequently, it is necessary to ensure operational safety of the dust-removal maintenance so as not to cause health damage from suction of the dust.
In the case of providing the scraping mechanism, the number of components is increased. As a result, a manufacturing cost of products would be increased, and replacement of the scraping mechanism would be regularly required, thus increasing a running cost.
Because a temperature of a combustion gas in the combustion treatment chamber is as high as about 1700° C., a heat-resisting material, such as alumina-base glass ceramic, is used for the cylindrical body that surrounds the combustion treatment chamber. However, the temperature of the combustion treatment chamber is high, and if a fluorine or chlorine gas exists, the inner surface of the cylindrical body would be corroded and wasted. Therefore, it is necessary to regularly replace the cylindrical body. Such replacement of the high-priced cylindrical body incurs a cost and requires time-consuming maintenance.